1. Field of the Invention
The invention relates to a coke manufacturing process according to which coal is introduced upstream of a slightly inclined rotary tubular oven, through which the product, in the course of its processing, moves from the upstream end to the downstream end, in which the calories required for carbonization are obtained by means of the combustion of part of the volatile constituents of the processed coal, by means of the introduction of air into the oven, the process being applied to the production respectively of pulverulent coke and of reactive coke in grain form, respectively from fines and coal grains containing more than 15% of volatile matter, with a swelling index ranging between 1 and 8, by means of carbonization between about 600.degree. and 1100.degree. C.
2. Description of the Prior Art
The coals of the type with which the invention is concerned cannot, in known manner, be carbonised unless use is made of complicated techniques whose object is to preserve them from mass agglutination as they pass through the plastic stage before resolidification. Thus, it is known to carbonize them in a bed of inert material such as sand or pulverulent coke, sometimes in the form of agglomerate. The heat required for carbonization is then supplied partly by the pulverulent solid and partly through gas combustion. But in practice the operator avoids taking as a starting material coal with too high a swelling index and with a volatile matter content in excess of 15%, that is to say coal of the type with which the invention is concerned.
It is known from German Pat. No. 243,141 to employ a process of coke manufacture from coal which is not normally usable for coking, in which the coal is subjected to limited degassing in a revolving oven. In this process the air and the combustion gas may be introduced at a certain distance from the outlet of the revolving oven. But if an attempt is made to apply this process to the coal referred to above, great adjustment difficulties have to be faced. The carrying out of the known process is characterised by a steady increase of the temperature of the processed product, from the inlet to the outlet of the oven, where it reaches the desired coking temperature. This technique cannot at present be applied to coal of the type with which the invention is concerned.
Indeed, if it is desired to apply such a process to the pyrolysis of products having a high volatile matter content, containing more latent heat than is required to heat the oven, it is observed that it is almost impossible to maintain a stable temperature regulation, even by distributing air inlets throughout the length of the oven. If, indeed, the flow of injected air decreases, the oven lacks heat, the product comes out less coked, and no longer possesses the desired quality. If the air flow increases, even very slightly, as a result, for example, of unavoidable stray inflows, the temperature of the flame rises very rapidly and therefore the coking temperature rises also, modifying the quality of the coke still further. But, in addition, as soon as the coke reaches the temperature at which it is completely degassed, the air finds no more gas to be burnt and advances into the oven until it finds some; the flame goes further down and the adjustment of temperatures is completely disturbed.
If agglutinating coal is used, there is in addition the tendency that the coal grains will stick together, forming "pellets" the cores of which are poorly coked and which may even lead to the clogging of the revolving oven.